1. Field of the Invention
The present invention relates to methods and apparatuses for repairing conduits. More particularly, the invention is directed to methods and apparatuses for repairing damaged, weakened, or leaking conduits that are located in areas to which it is difficult to gain access, for example, sewer pipes or other conduits that are located underground.
2. Description of Related Art
Conduit systems for carrying water or wastewater, for example, and other liquid and fluid conveyance systems, as well as conduit systems that house communication lines, for example, are typically located underground and, in general, are not easily accessible after installation. Over a period of time, such conduit systems become damaged, weakened, or otherwise begin to deteriorate and leak at the joints between adjacent conduit sections, for example. Such deterioration is caused, for example, by the settling of the surrounding earth adjacent the conduit system, by deterioration of the joints themselves over time, and/or by the growth of roots from trees and other plants.
In wastewater systems, wastewater can begin to leak from the damaged conduit and create problems of pollution, for example. In addition, damaged conduit sections invite the intrusion of rainwater into the system, adding to the volume of water carried to the treatment facility, thereby overburdening it. In conduits for communication systems, damage to the conduit can result in interruption of the service provided.
Further, deteriorated conduits for liquid conveyance systems, including sewer systems, that result in leaks can soak the surrounding terrain, sometimes creating sinkholes and exacerbating drainage problems. Further, service lines for gas, electricity, communications and other services, which themselves are not initially in need of repair, become damaged due to the re-settling of the water-saturated terrain in which they are located, thereby disabling same. Still further, support for buildings and bridges, for example, provided by the terrain in which a leaking conduit is located, can become weakened, thereby risking additional property damage or more serious concerns including loss of life.
A variety of solutions to the problem of repairing buried conduit sections have been proposed in the art. The most common solution, perhaps, involves excavation around the damaged conduit section and either the repair or replacement of the damaged section. However, excavation is time-intensive and, particularly in urban areas, it creates additional problems. For example, the destruction of overlying road surfaces is frequently necessary for gaining access to the damaged conduit section, thereby necessitating the re-routing of traffic and the subsequent need for re-building and resurfacing the road, adding to the cost of the repair. In addition, communication lines, water lines, gas lines, and other residential and/or commercial services that extend beneath the ground, can also be temporarily interrupted during the repair.
Methods have also been developed for repairing a damaged conduit section from within and without the need for excavation. Such methods include the mere application of a grout material for sealing cracks and joints, for example. It is also known in the art to re-line damaged conduit sections with a liner that is expanded from a coiled configuration to a final configuration in which the liner is secured against the inner surface of the damaged conduit section. A recent implementation of an internal conduit repair apparatus and method is disclosed in U.S. Pat. No. 5,119,862, issued on Jun. 9, 1992.
The latter-mentioned implementation includes the use of a compressible covering or gasket that is secured adjacent the outer surface of a sleeve liner to thereby form a composite liner/gasket combination. The sleeve and gasket combination is then coiled and inserted into a damaged conduit section, whereafter a "sewer plug", that is, an expandable air bag or, alternatively, any other internal means for expansion, forces the sleeve radially outwardly until the gasket is compressed against the inner surface of the damaged conduit section. After such compression, the internal expansion means is deactivated, whereby the sleeve is permitted to retract, that is, recoil slightly, thereby permitting the overlapping edges of the sleeve to become locked, due to a particular structural configuration of the edges.
Other examples of internal conduit repair systems are disclosed in U.S. Pat. No. 3,678,560, issued on Jul. 25, 1972; U.S. Pat. No. 3,700,265, issued on Oct. 24, 1972; U.S. Pat. No. 4,124,985, issued on Nov. 14, 1978; U.S. Pat. No. 4,346,922, issued on Aug. 31, 1982; U.S. Pat. No. 4,361,451, issued on Nov. 30, 1981; U.S. Pat. No. 4,647,072, issued on Mar. 3, 1987; U.S. Reissue Pat. No. 30,929, issued on May 11, 1982; and United Kingdom Patent Application No. 2,136,912, published on Sep. 26, 1984.
In U.S. Pat. No. 3,678,560 and a division thereof, namely, U.S. Pat. No. 3,700,265, an internal pipe sealing device is described in which an inner retaining member is placed within an outer sealing member, the outer sealing member being a cylindrical elastic member against which the inner retaining member is expanded inside of a pipe joint, thereby to seal the joint.
In U.S. Pat. No. 4,124,985 and Reissue Pat. No. 30,929, by the inventor of the instant patent, a method of lining the interior of a conduit is disclosed in which hinged collapsible sections are expanded against the conduit by means of one or more air bags. After the collapsible liner section has been erected and put into position, grout or other filler material is then inserted between the liner section and the conduit wall.
A device for sealing the joint of large diameter pipes, such as gas mains and water mains, is disclosed in U.S. Pat. No. 4,346,922. The device includes a cylindrical member made of an elastic material for covering the inside periphery of the pipe joint and circular expanding members for expanding the cylindrical member against the pipe joint. Belt members, impregnated with a bonding agent, such as epoxy resin, are positioned on the outside peripheral surface of the cylindrical member, at its ends, whereby the bonding agent is squeezed out by pressure, thereby obtaining an airtight and watertight bond between the outside peripheral surface of the cylindrical member at both of its longitudinal ends and the inside peripheral surfaces of the pipes.
U.S. Pat. No. 4,361,451 discloses a process for internally lining a conduit by coating the inner wall of the conduit with a first resin, coating the outer wall of a sleeve with a second resin, thereafter expanding the sleeve against the inner wall of the conduit, and maintaining pressure until the resins have become polymerized.
A system for repairing damaged pipes internally is also described in U.S. Pat. No. 4,647,072. A repair sleeve is used, primarily for repairing damaged wastewater pipes in which access to a damaged pipe section is difficult. The repair sleeve is a flexible tubular member and is expanded against the damaged pipe with a spiral spring positioned within the flexible tubular member.
U.K. Patent Application No. 2,136,912 discloses the repair of a damaged underground pipe by wrapping a sleeve around a collapsible inflatable bag, impregnating the sleeve with resin and expanding the sleeve against the damaged pipe until the resin is set.
Although the above-mentioned methods are directed to the repair of underground or otherwise inaccessible conduits without significant excavation, certain disadvantages remain. For example, in the systems in which resin is employed, an expansion pressure must be applied until the resin is sufficiently set to permit the withdrawal of the expansion means.
In the embodiments in which a liner is not utilized, any sealing of cracks or joints with resin or grout are only good for the short term and, therefore, require subsequent retreatment.
Further, in certain of the embodiments in which a liner is utilized, internal pressure is applied against the damaged pipe section, during expansion of the sleeve against the interior of the damaged pipe, thereby risking additional damage or weakening of the conduit, which could necessitate subsequent repair.